1. Field of the Invention
The present invention relates to a variable displacement oil pump and in particular relates to a variable displacement oil pump in which a control oil pressure supplied to a variable displacement mechanism is regulated by a control valve of an electronic control type.
2. Description of Related Art
As an oil pump of an engine, Japanese Patent Application Publication No. 2012-132356 (JP 2012-132356 A) discloses an internal gear oil pump in which an oil suctioned from a suction port is discharged to a discharge port by rotation of an inner rotor (drive rotor) and an outer rotor (driven rotor) that mesh with each other.
The above oil pump includes an adjustment ring that holds the outer rotor from a circumference in a rotatable manner in the housing, and, when the adjustment ring is displaced by receiving oil pressure that is led to a pressurizing space in the housing, relative positions of the inner rotor and the outer rotor to the suction port and the discharge port are changed. Accordingly, it is possible to change a discharge amount (a so-called displacement, and may hereinafter be referred to as a pump capacity) per rotation of an input shaft.
In addition, as disclosed in the paragraphs 0043 to 0047 (another embodiment) as well as FIGS. 3 and 4 of the same document, a control space (oil pressure chamber) is provided adjacent to the pressurizing space in the housing, and control oil pressure is regulated and supplied to the control space from a control valve of an electronic control type to generate a force to assist in displacing the adjustment ring as described above.